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ANDERSON COOPER, CNN ANCHOR: Laci Peterson. As we mentioned at the top of the hour, CNN has confirmed that Laci Peterson's husband has been arrested in San Diego. California state crime lab is working 24/seven to determine if the remains that washed ashore this week are those of Laci Peterson and her unborn son. We are joined on the telephone right now by Candace Rocha, Laci Peterson's cousin. Ms. Rocha, thank you so much for joining us.

CANDACE ROCHA, LACI PETERSON'S COUSIN: You're welcome.

COOPER: Your thoughts upon hearing that Scott Peterson has been arrested?

ROCHA: Relieved, happy, joy. I hope we get justice done now. I hope justice will be served right.

COOPER: You believe Scott Peterson killed Laci?

ROCHA: I do believe so, yes.

COOPER: What -- what went through when you heard Monday that -- well, Sunday that a body had been found and Monday that a body had been found nearby. What -- what went through your mind? What went through your family's hearts?

ROCHA: A lot of mixed emotions, mixed feelings. Happy ones, sad ones. Actually we wanted to find Laci and the baby both alive and well, which we didn't. But at least we've found them and we can put them at rest now and at peace.

COOPER: Do you believe, in fact, that the two remains found on Sunday and Monday are that of Laci Peterson?

ROCHA: I do believe so, yes.

COOPER: And what makes you think that?

ROCHA: Oh, just because there's been no other missing people that are -- that would be pregnant with a full-term baby. You know, that have reported missing and I have a gut feeling and an instinct and that it's my cousin Laci and her baby, Connor.

COOPER: And -- and obviously you know the statement made by one of the prosecutors who said that he had the same gut feeling. Have you heard anything from investigators? ROCHA: No, I have not.

COOPER: How did you hear about the arrest of Scott Peterson?

ROCHA: My cousin Dennis called and told us. His -- her father.

COOPER: Do you know if anyone in your family was informed by -- by the state or it was something they just heard about on TV or radio?

ROCHA: I do believe that Sharon, Laci's mother, received a phone call from the police, I believe.

COOPER: What happens now? I mean, this -- this has been going for so long. I -- I simply cannot imagine what you and your family have been going through. It's just got to be every day a different kind of a nightmare. What...

ROCHA: Yes.

COOPER: What are your thoughts now?

ROCHA: Well, now she's home at least with us and we can lay her to rest and lay Connor to rest and hopefully justice will be done and stuff and, you know, and the right manner of justice will be taken care of and I just hope he pays for what he did to her and his baby. A terrible thing that was done to her and the baby.

COOPER: Are you confident that the state has the evidence they need, if in fact that is what they are going to charge Scott Peterson with?

ROCHA: I believe so, yes. I think so.

COOPER: You have confidence in --in investigators as you've seen so far and the prosecutors?

ROCHA: Oh, yes.

COOPER: Candace Rocha, I don't want to probe too deeply because I -- it's got to be just an extraordinarily difficult day for you and I appreciate you -- you spending time with us on the phone right now. Candace Rocha, cousin of Laci Peterson, please send our best to your family. Thanks very much.

We are joined now by Dr. Cyril Wecht, a forensic pathologist. As Allegheny County's coroner, he is an expert on forensic pathology and he joins me from Pittsburgh.

Dr. Wecht, thanks for being with us.

DR. CYRIL WECHT, CORONER OF ALLEGHENY CO.: Good evening.

COOPER: Again, I want to just caution viewers -- I read a little bit of preinterview that was done with you and some of the stuff that was talked about in the preinterview is quite graphic and I want to give a caution to viewers that -- that in discussing this we certainly mean no disrespect and at this point we are just trying to get as much information and glean as much intelligence as we can on this ongoing investigation.

Dr. Wecht, two bodies discovered, two remains found, relatively close to each other, a day apart or so, the bodies -- the remains have been in water for a very long period of time. What can investigators determine?

WECHT: Well, you can determine the sex. You can determine the race. You can determine approximate age, including the fetus, and then you have to move, obviously, to more specific identification, namely, who are these two people?

And, as the cousin just said, and it makes all the sense in the world, it has been commented upon by many people, this is not just a body recovered from water and you might say, Well aren't there other people, possibly who have drowned in some fashion or so on? You have here a woman who apparently was pregnant, as I understand it, based upon at least one or two articles of clothing, customarily worn by pregnant women.

By now the physical examination has been conducted by the forensic pathologist and they may have found other evidence, pathologically of pregnancy. I cannot know that. But that is possible. And the fetus, of course, they can make some determinations.

I think that the specific identification will be made by DNA. The baby will be tied into the mother with mitochondrial DNA, this baby from that woman, that's a matrilinial descent, that's a particular kind of DNA, child to mother, like in Saddam Hussein's case with that half-brother who shares the same mother, they can do mitochondrial DNA there.

They'll also have blood, I'm sure, that they collected previously from Scott Peterson. They'll tie that in and they'll be able to get a complete DNA for identification of the baby as the child of Laci and Scott Peterson.

You then move to cause of death. I believe -- I hope I'm wrong -- that they will not be able to determine the cause of death.

COOPER: Why do you say that?

WECHT: The head is missing. It's highly unlikely that she was shot or stabbed and that there will be definitive bony (ph) injuries that can be attributed to a gun shot wound or stab wounds.

Strangulation is probably not ascertainable because of the absence of the head, which probably means that the structures high up in the neck, the hyoid bone, the small U-shaped bone beneath the chin, the Adam's apple, the thyroid cartilage, the (UNINTELLIGIBLE) cartilage immediately beneath it, they probably are absent. And in many cases of strangulation anyway, they are not fractured even if they were there. Suffocation, you would not be able to tell. And the drowning, you cannot tell definitively. That is an exclusionary diagnosis that we can only arrive at after having ruled out everything else.

So I do not believe that in a definitive scientific fashion they will be able to say that Laci Peterson died from this or that. The baby, obviously, was in utero and the baby died because the mother died. The baby's circulation and nutrition, of course, comes from the mother. So there, the cause of death can be inferred because of the mother's death.

The manner of death can be inferred too, namely homicide by virtue of the way in which the bodies are found, the places in which they are found. You have not ruled out other possibilities of accident or suicide and I don't believe that for one second, please understand. But I'm just saying that people can drown accidentally, they can commit suicide by going into the water.

So these are the things that -- who knows? The defense may play out should this case ever go to trial. They'll say, Hey, how can you prove that Scott Peterson killed these people? You don't know the cause of death. How can you prove that he killed this woman and threw her into the water?

Now, I don't know, Anderson -- there may be physical evidence out there. I've not read or heard about it. This has been going on for four months. They've gone back to his home a couple of times. They've collected dozens and dozens of bags and hundreds if not thousands of pieces of evidence. What they are and what they all cumulatively lead to, I do not know at this time.

COOPER: There are things that water does to -- to remains, as you point out that make it more difficult to identify, but also may preserve other aspects of it.

There are -- there are two things that -- that I sort of want to ask about. I really don't want you to go into too much detail because I -- I kind of know the answers and it's pretty graphic stuff.

But two things that -- that I think the layman would point to as -- as curious. One, the -- the -- the -- the -- the child's body, the fetus found separate from -- from -- from the adult's body and also the fact of decapitation that -- you believe that did not necessarily happen before death. That might have happened post-mortem.

WECHT: Yes. All right, let me briefly and I hope, in a relatively not too ghoulish fashion describe and explain both of these phenomena.

The baby was inside the uterus. The tissues of the mother begin to swell and decompose, soften, even the bony structures in a way soften, the lower uterine segment, the cervix which is closed and tight normally in pregnancy, loosens. Water comes up into the uterus. The baby is literally swimming in the environmental water.

After a while, when sufficient decomposition has taken place between baby and mother, the baby is loosened, attached only by the umbilical cord and quite literally floats out of the uterus into the water. That's how that baby got into the water. Insofar as the missing head and we have heard legs, if this be true, my own theory -- and it is conjecture -- but I do not believe that this body was dismembered, simply because I don't see any purpose having been attained by whoever did this. Every sixth grader in America knows identification is done by DNA and you don't have to look at the face or have the dental records.

I think that weights were attached to this body. Someone did not throw that body into the water and let it float around, expecting or anticipating, certainly, that it could be discovered the very next day. That body was weighted, and I believe that it was -- understood, in the perpetrator's mind that that body would never be seen again. That heavy weight had to be affixed to the body by a wire or a rope, most probably around the neck, another one probably around the lower torso. After a period of time, with the tissue softening, loosening, decomposing, that heavy weight remaining, the tension and the stress pulling down on the wire or the rope, and you have disarticulation of the head and of the lower extremities. That is why I believe the body is in the condition that it is.

COOPER: All right, Dr. Cyril Wecht, I appreciate you joining us for your insights. Forensic pathologist from Allegheny County, I appreciate you joining us.